Liquid desiccant based dehumidification and cooling system

ABSTRACT

A liquid desiccant system including a high desorber, a low desorber, and an absorber that are in fluid communication with a working solution, where the high desorber provides rejected water vapor from the working fluid for condensation in a condenser of the low desorber that provides heat for rejection of additional water from the working solution in the low desorber effectively multiplying the heat provided for desorption. The low desorber provided the concentrated working solution to the absorber where water from ambient air is condensed into the concentrated working solution to provide a dilute working solution within a working solution conduit of the absorber that is thermally coupled to an internal cooler of the absorber. In some embodiments, the working solution can be an aqueous solution of at least one ionic liquid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalApplication Ser. No. 62/598,568, filed Dec. 14, 2017, titled “LiquidDesiccant Based Dehumidification and Cooling System,” the disclosure ofwhich is hereby incorporated by reference in its entirety.

STATEMENT OF GOVERNMENT SUPPORT

This invention was made with government support under grant numberDE-EE0006718, awarded by the Department of Energy (DOE). The governmenthas certain rights in the invention.

BACKGROUND

Cooling systems are a pillar of modern civilization that have greatlyenhanced our standard of living and enabled the development of largepopulation centers, even in very harsh climates. Globally, coolingsystems consume a large fraction of the electrical energy supply and area significant contributor to peak power load. As demand for airconditioning rapidly increases in emerging economies, cooling systemsare expected to further strain the power grid. The energy consumed inresidential and commercial buildings represents over one-third of globaland approximately 40% of the total US energy consumption. This, withinthe US, represents approximately 38 quadrillion British thermal units(quads) of primary energy. Within the US residential and commercialbuilding sector, water heating (3.8 quads) and heating, ventilation andair conditioning (HVAC) (15.2 quads) represent half of the energyconsumed. It is estimated that the global air-conditioning energy demandwill increase by 72% by 2100, due to a significant increase in airconditioning demand in developing countries. The ability to meet even aportion of the increased demand for electricity will be a significantchallenge, requiring trillions of dollars in investments in electricitygeneration and transmission infrastructure. While multiple sources,natural gas, electricity, fuel oil, propane, solar, etc., of energy areused for water heating, electricity is the predominant source of energyused for HVAC applications. These systems are also responsible for therelease of high global warming potential (GWP) refrigerants. There arevery limited low GWP refrigerants replacement options for existing highGWP refrigerants highlighting a pressing need to reduce reliance on thevapor compression systems that currently dominate the cooling market. Toadequately slow the growth in energy consumption and environmentalimpacts of cooling systems, changes are required to both buildings andheating, ventilation, and air conditioning (HVAC) systems. To date, theimplementation of building changes using energy saving measures such asaddition of more insulation, better windows, and sealed air barriershave outpaced changes in the associated HVAC systems. The result,particularly in small buildings ill-equipped to actively controlhumidity, is increased humidity levels and poor Indoor Air Quality(IAQ).

BRIEF SUMMARY

Embodiments of the invention are directed to liquid desiccantdehumidification systems (LDDSs), for instance double-effect LDDSs,having at least one high desorber, at least one low desorber, and atleast one absorber. The high desorber is configured with the lowdesorber for condensation of water evaporated from a working solutionwithin the high desorber in a condenser of the low desorber. The workingsolution from the low desorber is configured with the absorber forcondensation of water from ambient air into the working solution withina working solution conduit of the absorber. The absorber includes aninternal cooler. In some embodiments, the working solution is an aqueoussolution that includes at least one ionic liquid (IL). The double-effectLDDS can have a high heat exchanger thermally coupling portions of theworking solution that is situated downstream of the high desorber,upstream of the low desorber, and downstream of the absorber withrespect to the flow of the working solution in the double-effect LDDS.The double-effect LDDS can have a low heat exchanger thermally couplingportions of the working solution that is situated downstream of the lowdesorber and upstream of the absorber with respect to the flow of theworking solution in the double-effect LDDS. The double-effect LDDS caninclude a low heat exchanger thermally coupling portions of the workingsolution that is situated downstream of the low desorber, upstream ofthe absorber, and upstream of the high desorber with respect to the flowof the working solution in the double-effect LDDS. Advantageously, theIL can be non-crystalizable.

In some embodiments, a desorber can be configured to increase theconcentration of desiccant in the working solution. A desorber can beconfigured to desorb water from a heated working solution comprising adesiccant and water vapor. In some embodiments, the desorber cancomprise a desorber housing comprising a first housing portion and asecond housing portion, the first housing portion at least partiallydefining a first portion of an inner volume of the desorber housing andthe second housing portion at least partially defining a second portionof the inner volume of the desorber housing. In some embodiments, afirst plurality of diffusion plates disposed within the first portion ofthe inner volume of the desorber housing, the first plurality ofdiffusion plates defining a first one or more apertures therethrough. Insome embodiments, a second plurality of diffusion plates disposed withinthe second portion of the inner volume of the desorber housing, thesecond plurality of diffusion plates defining a second one or moreapertures therethrough. In some embodiments, the first one or moreapertures are dimensioned and configured such that water vapor can bedirectly desorbed through the first one or more apertures at atemperature of between about the boiling point temperature of water(e.g., about 100° C.) and about a boiling point of the desiccant. Insome embodiments, the desorber being configured to directly desorb atleast a portion of the water vapor from the working solution in a stillair environment.

In some embodiments, the first housing portion can define a firstworking solution inlet port, a vapor outlet port, a water outlet port,and/or a first working solution outlet port. In some embodiments, thesecond housing portion defining a second working solution inlet port, aheat exchange fluid inlet port, a heat exchange fluid outlet port,and/or a second working solution outlet port. In some embodiments, eachdiffusion plate of the first plurality of diffusion plates can besubstantially rectangular in shape. In some embodiments, each diffusionplate can include a first aperture offset in a radial direction from aradial axis of each diffusion plate of the first plurality of diffusionplates. In some embodiments, a second aperture offset in an oppositeradial direction from the radial axis of each diffusion plate of thefirst plurality of diffusion plates. In some embodiments, the secondaperture defined parallel to the first aperture and having the samedimensions.

In some embodiments, the first plurality of diffusion plates are stackedtogether to form a first diffusion plate stack. In some embodiments, thefirst diffusion plate stack at least partially defining a first fluidflow path through the first housing portion of the desorber housing, Insome embodiments, the first aperture and the second aperture can beconfigured to reduce the first fluid flow path such that water vapordiffuses more rapidly through the first diffusion plate stack. In someembodiments, each diffusion plate of the second plurality of diffusionplates is substantially rectangular in shape. In some embodiments, eachdiffusion plate of the second plurality of diffusion plates can includea third aperture defined linearly through each plate of the secondplurality of diffusion plates in an axial direction and centeredradially. In some embodiments, the second plurality of diffusion platesare stacked together to form a second diffusion plate stack. In someembodiments, the second diffusion plate stack at least partially definesa second fluid flow path through the second housing portion of thedesorber housing greater than the first fluid flow path through thefirst housing portion of the desorber housing. In some embodiments, thesecond diffusion plate stack can be configured to exchange thermalenergy with a heat exchange fluid.

In some embodiments, the working solution comprises an ionic liquid (IL)and water. In some embodiments, the IL is non-crystalizable. In someembodiments, the IL can include one or more of Evonik CrysCo Plus 2200,Evonik CrysCo Plus 2630, piSorb 275, and Sorbionic4,1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide,1-ethyl-3-methylimidazolium bis (trifluoromethyl-sulfonyl)amide,tetra-nbutylphosphonium trifluoromethanesulfonyl leucine,N-alkyl-N,N-dimethylhydroxyethylammoniumbis(trifluoromethane)sulfonylimidelithium bromide, lithium chloride, calcium chloride,combinations thereof, or the like.

A method for increasing a concentration of the desiccant in the workingsolution and cooling the working solution can be carried out using thedesorber described above. In some embodiments, the method can includecharging the heated working solution into the first portion of the innervolume of the desorber housing. In some embodiments, the method caninclude communicating the heated working solution along the first fluidflow path such that at least a first portion of water vapor desorbs fromthe heated working solution and is communicated out of the desorber,forming a concentrated working solution. In some embodiments, the methodcan include communicating the concentrated working solution from thefirst portion of the inner volume of the desorber housing into thesecond portion of the inner volume of the desorber housing. In someembodiments, the method can include communicating the first concentrateworking solution along the second fluid flow path such that the heatexchange fluid removes heat from the concentrated working solution.

According to other embodiments, an LDDS can include an absorberconfigured to absorb water from a process air (i.e., to dehumidify theprocess air). In some embodiments, the absorber plate can include acentral channel having a first surface and a second surface. In someembodiments, a first desiccant solution channel having a first surfaceand a second surface and configured to communicate a first portion ofthe desiccant solution therethrough. In some embodiments, the firstsurface of the first desiccant solution channel can be coupled to thefirst surface of the central channel. In some embodiments, the firstsurface of the first desiccant solution channel can be an engineeredsurface configured to slow down the spread of the first portion of thedesiccant solution as it is communicated across the first surface. Insome embodiments, the first surface of the first desiccant solutionchannel can include solid features, apertures therethrough, or the like.In some embodiments, a plurality of fins or other solid features can bedisposed on the first surface of the first desiccant solution channel.In some embodiments, the first surface of the first desiccant solutionchannel can be hydrophilic. In some embodiments, a first membrane, forinstance a hydrophobic membrane, can have a first surface and a secondsurface. In some embodiments, the second surface of the first membranecan be fluidically coupled to the desiccant solution channel. In someembodiments, the first surface of the first membrane and the firstportion of the desiccant solution can be configured to absorb watervapor from process air nearby the first membrane. In some embodiments, asecond desiccant solution channel can have a first surface and a secondsurface. In some embodiments, the second desiccant solution channel canbe configured to communicate a second portion of the desiccant solutiontherethrough. In some embodiments, the first surface of the seconddesiccant solution channel can be coupled to the second surface of thecentral channel. In some embodiments, the first surface of the seconddesiccant solution channel can be an engineered surface configured toslow down the spread of the first portion of the desiccant solution asit is communicated across the first surface. In some embodiments, thefirst surface of the second desiccant solution channel can include solidfeatures, apertures therethrough, or the like. In some embodiments, aplurality of fins or other solid features can be disposed on the firstsurface of the second desiccant solution channel. In some embodiments,the first surface of the second desiccant solution channel can behydrophilic. In some embodiments, a second membrane, for instance ahydrophobic membrane, can have a first surface and a second surface. Insome embodiments, the second surface of the second membrane can befluidically coupled to the desiccant solution channel. In someembodiments, the first surface of the second membrane and the secondportion of the desiccant solution can be configured to absorb watervapor from process air nearby the second membrane.

All components of the absorber can include or be formed from a polymermaterial. The internal cooler can be a conduit of cooling watercontacting the working solution conduit of the absorber and can besituated within a closed loop flow path comprising a cooling fluid. Theclosed loop comprises a fluid radiator for cooling the cooling fluid bythe ambient air. The internal cooler can be an evaporator connected to awater source, wherein the water from the water source evaporates in theinternal cooler. The high desorber can be coupled to a heater by aheating fluid. The absorber can be constructed of one or more polymers.

In some embodiments, the desiccant solution can include an ionic liquid(IL), such as a non-crystalizable IL. In some embodiments, the IL caninclude one or more of Evonik CrysCo Plus 2200, Evonik CrysCo Plus 2630,piSorb 275, and Sorbionic4, 1-butyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)amide, tetra-nbutylphosphoniumtrifluoromethanesulfonyl leucine,N-alkyl-N,N-dimethylhydroxyethylammoniumbis(trifluoromethane)sulfonylimidelithium bromide, lithium chloride, calcium chloride,combinations thereof, or the like. In some embodiments, the centralchannel can be a heat exchange channel configured to communicate a heatexchange fluid therethrough. In some embodiments, the first surface ofthe first desiccant solution channel can be thermally coupled to thefirst surface of the central channel. In some embodiments, the firstsurface of the second desiccant solution channel can be thermallycoupled to the second surface of the central channel. In someembodiments, the absorption of water from the process air nearby thefirst membrane, e.g., a first hydrophobic membrane, and the secondmembrane, e.g., a second hydrophobic membrane, can cause the process airto heat the heat exchange fluid being communicated through the heatexchange channel.

All components of the absorber can include or be formed from a polymermaterial. The internal cooler can be a conduit of cooling watercontacting the working solution conduit of the absorber and can besituated within a closed loop flow path comprising a cooling fluid. Theclosed loop comprises a fluid radiator for cooling the cooling fluid bythe ambient air. The internal cooler can be an evaporator connected to awater source, wherein the water from the water source evaporates in theinternal cooler. The high desorber can be coupled to a heater by aheating fluid. The absorber can be constructed of one or more polymers.

In some embodiments, a method of dehydrating air can be carried outusing an absorber such as the absorber described above. In someembodiments, the method can include communicating a first portion of theworking solution through the first desiccant solution channel and asecond portion of the second desiccant solution channel. In someembodiments, the method can include disposing process air nearby thefirst membrane and the second membrane such that water vapor is absorbedfrom the process air into the first and second portions of the desiccantsolution. In some embodiments, the method can include communicating aheat exchange fluid through the central channel such that, during theabsorption of water from the process air, the process air can heat theheat exchange fluid. In some embodiments, the desiccant can include anionic liquid, for instance a non-crystalizable ionic liquid. In someembodiments, the ionic liquid can include one or more of1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide,1-ethyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)amide,tetra-nbutylphosphonium trifluoromethanesulfonyl leucine,N-alkyl-N,N-dimethylhydroxyethylammoniumbis(trifluoromethane)sulfonylimide, or the like.

In some embodiments, a liquid desiccant dehumidification system (LDDS)can include an absorber configured to communicate water vapor from ahumid air flow into a first concentrated desiccant solution to form adilute desiccant solution. In some embodiments, the first concentrateddesiccant solution can include an aqueous solution of at least one ionicliquid and being capable of absorbing water. In some embodiments, afirst heat exchanger can be thermally coupled to the dilute desiccantsolution such that heat generated during communication of water vaporfrom the humid air flow into the concentrated desiccant solution can beexchanged with a first exchange medium. In some embodiments, the LDDScan further include a first desorber fluidically coupled to the absorberand thermally coupled to the first heat exchange medium. In someembodiments, the first desorber can be configured to heat the dilutedesiccant solution in a stack of desorption plates to desorb water vaporfrom the dilute solution to concentrate the dilute desiccant solutioninto the concentrated desiccant solution. In some embodiments, the firstdesorber having an operating temperature of between about the boilingpoint temperature of water (e.g., about 100° C.) and the boiling pointtemperature of one or more desiccants.

In some embodiments, the LDDS can further include a second heatexchanger thermally coupled to the first desorber such that thermalenergy from the first desorber can be conducted into a second exchangemedium. In some embodiments, the LDDS can further include a seconddesorber fluidically coupled to the first desorber such that theintermediate desiccant solution can be communicated therebetween andthermally coupled to the second heat exchange medium. In someembodiments, the second desorber can be configured to desorb at least aportion of the water vapor from the dilute desiccant solution, therebydesorbing water vapor from the dilute desiccant solution to form asecond concentrated desiccant solution having substantially the sameconcentration of ionic liquid as the first concentrated desiccantsolution.

Another embodiment of the invention is directed to a dedicated outdoorair system (DOAS), including at least one double-effect LDDS and atleast one air conditioning (HVAC) unit. At least one evaporator of aHVAC unit is in thermal communication with air dried by the absorber ofthe double-effect LDDS. The evaporator of a HVAC unit can be thermallycoupled to the internal cooler of the absorber. The condenser of theHVAC unit can be thermally coupled with at least one of the highdesorber and the low desorber.

Another embodiment of the invention is directed to a method fordehydrating ambient air by contacting ambient air with a concentratedworking solution in an absorber of a double-effect LDDS, condensing thewater in the ambient air in the concentrated working solution to form adilute working solution, and evaporating the water from the diluteworking solution in the high desorber and the low desorber.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a schematic for a prior art single effect liquid desiccantdehumidification system (LDDS), according to an embodiment.

FIG. 2 is a block diagram illustrating a double-effect LDDS, accordingto an embodiment.

FIG. 3 shows a schematic for a double-effect LDDS for coupling with aHVAC system, according to an embodiment.

FIG. 4A shows a heat pump water heater system for residential use,according to an embodiment.

FIG. 4B shows an energy efficient, cost-effective separate sensible andlatent cooling (SSLC) HVAC system implemented as a double-effectabsorption cycle for residential use, according to an embodiment.

FIG. 5A shows a schematic of an element of an all polymer absorber foruse in a double-effect LDDS, according to an embodiment.

FIG. 5B shows a drawing of a four absorption surfaces polymer absorbercoupling two elements into an absorber for use in a double-effect LDDS,according to an embodiment.

FIG. 5C shows a decorated spreading conductive surface for maintaining athin Ionic Liquid (IL) solution film over the surface for effectiveabsorption and heat transfer to the cooling medium for use in adouble-effect LDDS, according to an embodiment.

FIG. 5D shows a vapor permeable membrane for containing the IL solutionfilm of the absorber for a double-effect LDDS, according to anembodiment.

FIG. 6A shows a compact double desorber, according to an embodiment.

FIG. 6B shows an exploded view of the compact double desorber accordingto FIG. 6A.

FIG. 6C shows horizontal cross-sections of the compact double desorberaccording to FIG. 6A.

FIG. 6D shows vertical cross-sections of the compact double desorberaccording to FIG. 6A.

FIG. 7 shows a plot of the vapor pressure of solutions for absorption ofwater for use in LDDS systems, for various IL solutions and conventionalLiBr solution at various concentrations.

FIG. 8 shows a plot of effectiveness vs. the number of transfer units(NTU) for a plate heat exchanger that can be used in the double-effectLDDS, according to an embodiment.

FIG. 9 shows a schematic for a double-effect LDDS, according to anembodiment.

FIG. 10 show a schematic (L) and a photograph (R) for a high desorberfor use in a double-effect LDDS, according to an embodiment.

FIG. 11 shows a schematic for a configuration of the high and lowdesorbers of a double-effect LDDS, according to an embodiment.

FIG. 12 shows a schematic for a configuration of the high and lowdesorbers of a double-effect LDDS, according to an embodiment.

FIG. 13 shows a schematic for a configuration of the high and lowdesorbers of a double-effect LDDS, according to an embodiment.

FIG. 14 shows a schematic for a configuration of the absorber and itscooling using ambient conditions of a double-effect LDDS, according toan embodiment.

FIG. 15 shows a schematic for a configuration of the absorber andutilization of recovered water products from the low desorber of adouble-effect LDDS, according to an embodiment.

FIG. 16 shows a schematic for a configuration of the absorber andutilization of recovered water products from the low desorber of adouble-effect LDDS, according to an embodiment.

DETAILED DISCLOSURE

The challenge of high humidity levels is not limited to low-loadbuildings. Buildings in hot and humid climates have always had thischallenge. When significant humid fresh air is used, relative humidity(RH) can reach unacceptable levels even with the use of a dedicateddirect expansion (DX) dehumidification (DH) system. This challenge willbe exacerbated in residential buildings with the implementation ofASHRAE Standard 62.2-2016 ventilation, as it will create a new demandfor supplemental dehumidification units. Although it is well known thatthe latent load associated with fresh air treatment is always higherthan the sensible load in much of the US, it can be nearly half of thetotal building load in hot and humid climates. Measurement of loaddistribution in a 3-story 225-person office building in Tampa, Fla.showed that latent load due to ventilation accounted for 45% of theentire building load, leading to a sensible heat ratio (SHR) of lessthan 0.45 when all latent loads were considered. In the off-peakconditions, the situation can get much worse, since sensible loaddeclines proportionally with the outdoor temperature while latent loaddoes not, leading to a SHR of zero.

The trend of the SHR towards zero exacerbates the need to dry theventilation air in a hot and humid climate before mixing it with thereturn air, because the existing DX cooling systems are not capable ofhandling such a high latent load level. The existing vapor compressioncooling process capability set by its operation principle, whichrequires sub-cooling of air to condense moisture with a thermostatdriven demand and on/off cycling, is limited to a SHR range of 1 to0.65. Systems augmented with absorbents, such as hybrid DX and desiccantwheel systems, can extend this range with series regenerationconfiguration to an SHR of between about 0.4 and about 0.45.

The fundamental dehumidification principle of DX systems is thecondensation of air moisture, where the inability to effectively handleincreased indoor moisture levels have resulted in contaminated HVACunits as well as the creation of indoor environments that result in thedegradation of occupant's health. Poor IAQ leads to inefficient workenvironments and increases risk of respiratory infections and allergies.It is estimated that the potential annual savings and productivity gainsfrom improved IAQ in the United States can be as high as $14 billionfrom reduced respiratory disease, $4 billion from reduced allergies andasthma, $30 billion from reduced sick building syndrome, and $160billion from direct improvements in worker performance that areunrelated to health. Experimental studies on airborne-transmittedinfectious bacteria and viruses have shown that the survival rate orinfectivity of these organisms is minimized by exposure to relativehumidity levels between 30 and 60%, with 50% being the optimal point.This range of relative humidity is not currently achievable in allbuildings, particularly in hot and humid climates, using typical vaporcompression (VC) systems.

To significantly impact the energy profile of HVAC systems, systems mustbe configured for building specific applications and climate, as well asthe use of a variety of technologies and fuel types (electricity, gas,solar, etc.). The ability to separately handle building sensible andlatent heat load facilitates the cost-effective tailoring of buildingHVAC configurations, and the ability to address the poor Indoor AirQuality (IAQ) issues resulting from poor indoor humidity control. Asignificant change in the energy consumption profile for building HVACand water heating systems requires new energy efficient technologies.These technologies should represent a leap in energy efficiency,breaking the cycle of small incremental efficiency improvements ofexisting technology.

The vapor compression or direct expansion (DX) process is not capable ofhandling sensible and latent heat separately. To remove moisture fromair, existing systems must often overcool air to saturation conditions.The ability to efficiently reduce the air moisture content withoutcooling it can enable much more efficient HVAC systems capable ofhandling the sensible and latent loads separately (allowing independentcontrol of humidity and temperature levels in buildings). Liquiddesiccant technology can play a key role in achieving this objective ifhigh efficiency, low-cost, scalable and robust systems can be developed.However, this potential has not materialized despite a few decades ofresearch and development. Current single-effect liquid desiccanttechnology has a low energy efficiency (a COP of 0.6-0.7) and needs ameans of removing the absorber heat; for example, the evaporator of a DXsystem. The need for this secondary cooling system along with a lowdesiccant regeneration efficiency negate the energy saving benefit ofthe system, while increasing the HVAC system cost.

A conventional single effect liquid desiccant dehumidification system(LDDS) is shown in FIG. 1. A hygroscopic salt solution removes watervapor from the air in the absorber. The heat of phase change should beremoved from the absorber and heat is required to regenerate thedesiccant solution in the desorber. Unfortunately, implementation ofthis system has remained limited due to two factors: the cycle is lessenergy efficient than DX systems; and the requirement of a means ofremoving the absorber heat, typically a wet cooling tower (or anintegrated evaporative cooling medium) or coupling with the evaporatorof a DX system. To provide energy savings, the desiccant regenerationheat must be free, provided by the condenser of a DX system or anengine, fuel cell, or other heat source. To this end a superiordesiccant dehumidification system is desirable.

According to an embodiment of the invention, a system fordehumidification and/or air conditioning can enable the implementationof absorption systems for buildings and industrial applications. Thisnew architecture can reduce or eliminate the need for hermeticcomponents leading to simpler designs with reduced complexity therebygreatly reducing the system cost. The implementation of thisarchitecture can be dependent on membrane-based plate-and-frame heatexchangers, the implementation of ionic liquids (ILs) as the cycleabsorbent as well as other technologies to maximize system efficiencyand performance. The membrane-based plate-and-frame heat exchangers mayreduce the component size and cost while fully containing the absorbent.In these heat exchangers, 3D surface structures can be utilized tocontrol the absorbent film thickness and induce mixing to enhance masstransfer.

According to an embodiment of the invention, a double-effect semi-openliquid desiccant system (LDDS) that can be a standalone system orcoupled to other systems to implement sensible and latent cooling anddrying, for example as shown in FIGS. 2 and 3, can from a primary energyperspective approximately double the energy efficiency of a LDDS. Thedouble-effect semi-open LDDS is a standalone system that is 40-50% moreefficient than the average DX system for dehumidification within the US.The semi-open arrangement allows for recovery of all the absorbed waterand its use for absorber cooling in an integrated evaporative coolingconfiguration.

Briefly, LDDSs operate by removing moisture from the inlet air in adehumidification unit or an absorber unit using a desiccant (e.g., asalt, a silica gel, or the like) to absorb water vapor from process air,forming a dilute solution comprising the desiccant and water. Masstransfer in the system occurs due to vapor pressure differences, andheat is given off during the condensation of water from water vapor andduring heat exchange due to mixing. The dehumidified process air canthen be cooled and/or introduced into the indoor space. The dilutesolution, now comprising the desiccant and an elevated concentration ofwater condensed from the water vapor in the inlet air, can beregenerated. The dilute solution can be regenerated by first passing thedesiccant solution through a first liquid-liquid heat exchanger and thena heating coil to raise the temperature of the dilute solution, suchthat water from the dilute solution migrates from the dilute solutiondue to a vapor pressure differential, forming a concentrated solutioncomprising the desiccant and relatively little water. The concentratedsolution can then be passed through a second liquid-liquid heatexchanger and then a cooling coil to lower the temperature of theconcentrated solution, and be used again in the dehumidification processto remove water vapor from the inlet air.

FIG. 2 illustrates such a LDDS (10) comprising an absorption system 100and a desorption system 110. In some embodiments, the LDDS 10 cancomprise a packed-bed absorption system, a plate heat exchanger system,a multi-stage boiler system, a collector/regenerator system,combinations thereof, or the like. The absorption system 100 can includean absorber 102 configured to receive an inlet air 12 (e.g., hot-humidoutdoor air), remove at least a portion of the water vapor from theinlet air 12 to form an outlet air 14, and communicate the outlet air 14out of the system. Optionally, the LDDS 10 or a component thereof (e.g.,the absorber 102) can be configured to communicate at least a portion ofthe outlet air 14 to further processing unit such as a cooling system(not shown) such as an evaporative cooling tower, a central airconditioner, a heat pump, a room air conditioner, an evaporative cooler,a ductless mini-split air conditioner, a split system, a single-splitsystem, a multi-split system, a variable refrigerant flow (VRF) system,a variable refrigerant volume (VRV) system, a variable air volume (VAV)system, a constant air volume (CAV) system, combinations thereof, or thelike.

In some embodiments, the LDDS 10 can comprise a first vapor compressioncycle dealing with sensible cooling load and a second vapor compressioncycle to deal with latent cooling demand from indoor and outdoor air,otherwise known as a separate sensible and latent cooling (SSLC) system.In some embodiments, sensible and latent heat exchangers can be arrangedin sequence along the air processing flow direction. Return air can bemixed with outdoor fresh air before flowing into the sensibleevaporator. After it passes through the sensible evaporator, air flowcan be divided into two streams: one stream being sent to the reheatheat exchanger for pre-cooling, and processed through the latentevaporator while the other stream is bypassed. The air stream exitingthe latent evaporator can then be reheated through the reheat heatexchanger, and mixed with the second stream that was bypassed.

In some embodiments, the absorber 102 can comprise a plate or a web oranother such complex surface configured to communicate the liquiddesiccant solution across the surface of the absorber while the inletair 12 is communicated past the liquid desiccant, such as Evonik CrysCoPlus 2200, Evonik CrysCo Plus 2630, piSorb 275, and Sorbionic4,1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide,1-ethyl-3-methylimidazolium bis (trifluoromethyl-sulfonyl)amide,tetra-nbutylphosphonium trifluoromethanesulfonyl leucine,N-alkyl-N,N-dimethylhydroxyethylammoniumbis(trifluoromethane)sulfonylimidelithium bromide, lithium chloride, calcium chloride,combinations thereof, or the like. In some embodiments, the ionic liquidcan include one or more of 1-butyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazoliumbis(trifluoromethyl-sulfonyl)amide, tetra-nbutylphosphoniumtrifluoromethanesulfonyl leucine,N-alkyl-N,N-dimethylhydroxyethylammoniumbis(trifluoromethane)sulfonylimide, or the like. Further discussion of desiccants, the usethereof, and the implications for dehumidification efficiency in thesystems described herein are described further below.

Upon contact with the liquid desiccant, at least a portion of the watervapor in the inlet air 12 condenses out of the inlet air 12 and goesinto solution with the liquid desiccant, forming the dilute solution andgenerating heat due to condensation. In some embodiments, the absorber102 can comprise a hollow plate or other structure such that an exchangemedium can heat the dilute solution. In some embodiments, the absorber102 can comprise an integrated absorber/evaporator cooling system. Insome embodiments, the absorber 102 can be configured to defuse the inletair 12 across a volume or surface area of desiccant material. In someembodiments, the absorber 102 can be configured to increase the surfacearea of liquid desiccant solution such that more inlet air 12 comes intocontact with liquid desiccant solution during operation of the absorber102.

In some embodiments, either the absorption system 100 and/or thedesorption system 110 can further include a condenser 104 configured tocondense water vapor from high relative humidity air into liquid water,giving off heat in the process. In some embodiments, the condenser 104can be configured to receive desorbed water vapor and provide water toan evaporative cooling system (e.g., the integrated absorber/evaporatorcooling unit). In some embodiments, the absorption system 100 canfurther include a first heat exchanger 106 configured to carry outliquid-liquid heat exchange between the strong solution from the seconddesorber 114, and the dilute solution from the absorber 102, in order toraise the temperature of the dilute solution. In some embodiments, afterheating the dilute solution, e.g., to above a threshold temperature, fora predetermined duration, or the like, the dilute solution can becommunicated to the desorption system 110.

The desorption system 110 can include a first desorber 112 configured toheat the dilute solution and directly desorb or diffuse a portion of thewater vapor from the dilute solution, through a porous plate stack orthe like such that the liquid desiccant concentration is increased,forming an intermediate solution. Whereas conventional desorptionprocesses require a low humidity air supply (i.e., a scavenger airsupply) to cause water or water vapor from dilute desiccant solutions toevaporate or desorb, embodiments of the desorption system 110 can carryout desorption of water vapor from the dilute desiccant solution withlow or no air introduced at relatively higher temperatures. Withoutwishing to be bound by any particular theory, the direct desorption ofwater vapor from the dilute desiccant solution in a still airenvironment may result in a more thermally efficient process because theevaporative cooling of conventional air scavenging desorption processesis avoided, which means more of the thermal energy is retained in thesystem to be exchanged and put to work elsewhere in the process. In someembodiments, the heat can be captured by an exchange medium in a secondheat exchanger 116, the second heat exchanger 116 being in thermalcommunication with the dilute solution and/or the first desorber 112. Insome embodiments, at least a portion of the intermediate solution canthen be communicated to a second desorber 114.

In some embodiments, the second desorber 114 can be configured toreceive the intermediate solution and desorb at least a portion of theremaining water or water vapor from the intermediate solution, such asdescribed above with regard to the first desorber 112, forming theconcentrated solution. Once concentrated solution is formed at thesecond desorber 114, it has been regenerated for subsequent desiccationpurposes by the absorber 102. The desorbed water vapor from the seconddesorber 114 can be exhausted to the outdoors or communicated to thecondenser 104 such that water vapor can be condensed, from which theheat of condensation can be exchanged with a heat exchange medium andput to work elsewhere in the process.

As shown in FIG. 2, the first desorber 112 provides desorbed water vaporto the second desorber 114, which aids during regeneration of theintermediate solution to the concentrated solution by the seconddesorber 114. In some embodiments, the desorbed water vapor from thefirst desorber 112 can be used to cool the outlet air 14. In someembodiments, at least a portion of the desorbed water vapor form thefirst desorber 112 can be combined with at least a portion of thedesorbed water vapor from the second desorber 112 and communicated tothe condenser 104.

FIG. 3 illustrates a LDDS 20 comprising an integratedabsorber/evaporator cooling medium unit 202, a condenser 204 configuredto provide condensed water vapor to the integrated absorber/evaporativecooling unit 202 for evaporative cooling, a first heat exchanger 206and/or a second heat exchanger 208 configured to exchange the heat fromthe integrated absorber/evaporative cooling unit 202 with an exchangemedium. As water or water vapor is absorbed from process air by thedesiccant (e.g., liquid desiccant), the water or water vapor dilutes thedesiccant to form a dilute desiccant solution, which can be regeneratedby desorption processes. The LDDS 20 can include a first desorber 212configured to remove water from the dilute desiccant solution, formingan intermediate solution and causing cooling of at least one of theintermediate solution and the desorbed water vapor. The LDDS 20 canfurther include a second desorber 214 configured to receive at least aportion of the intermediate solution from the first desorber 212 andremove water from the intermediate solution, forming a concentratedsolution that has been at least substantially regenerated. The LDDS 20,similar to the LDDS 10 and others described through this disclosure, canbe classified as a semi-open system. One of the key differences betweenthe semi-open system (e.g., LDDS 20) and a conventional open system isthe addition of a condenser that condenses the vapor released from thedesorber, among other differentiating factors or elements. As describedherein, the desorber can be a single-plate desorber, a multi-platedesorber, or the like. In some embodiments, the desorber 212 and/or 214can be heated by a heating fluid, indirectly via solar thermalconfigurations, heated via direct firing from gas combustion, or thelike. The double-effect configuration allows the use of vapor generatedin the first desorber 212 for regeneration of solution in the seconddesorber 214. Without wishing to be bound by any particular theory, theuse of vapor generated in the first desorber 212 for regeneration of thedesiccant solution in the second desorber 214 may be at least partiallyresponsible for the higher cycle efficiency, for instance, since oneheat input step allows two solution regeneration steps. Furthermore,since the first desorber 212 may operate without the use of scavengerair for desorption/evaporation purposes with respect to the removal ofwater or water vapor from the desiccant solution, the cooling of thedesiccant solution associated with desorption/evaporation usingscavenger air can be avoided and the intermediate desiccant solutionneeds not be subsequently re-heated in order to be regenerated in thesecond desorber 214. In some embodiments, the condenser 204 can beconfigured to reject heat to ambient air. The condensate can then beused in an evaporative cooling process at the integratedabsorber/evaporative cooling unit 202 to cool process streams at theunit 202, such as the desiccant solution, the dilute desiccant solution,the process air, or the like. This evaporative cooling capacity canemploy greater than or equal to about 90% of the absorber heatrejection, with the heat of mixing being less than or equal to about10%. Depending on whether the ambient, at either peak or off-peaktemperature, or exhaust air is used for cooling the absorber, the systemmay or may not require makeup water, respectively.

This double-effect semi-open LDDS 20 represents a compact, efficient,robust, and cost-effective technology that can enable widespreadadoption and realization of significant energy savings, particularly inthe existing building stock and industrial dehumidification processes.The double-effect semi-open LDDS 20 can be configured and sizedappropriate for the required load in a variety of ways to addressspecific building/climate needs. In addition to using larger sizedcomponents and devices, a plurality of double-effect semi-open LDDS 20systems, components of the system, and/or portions of components can beemployed in a cooling system. Double-effect LDDSs (e.g., LDDS 10, LDDS20, etc.) can rapidly enter the retrofit market as a dedicated outdoorair system (DOAS), a stand-alone building latent load handling unit, asubstitute for the less-efficient and water-consuming element of liquiddesiccant cooling systems, or as a standalone or component of industrialdehumidification/drying systems.

In some embodiments, the double-effect semi-open LDDS 20 can include asemi-open absorption cycle, a compact membrane-based absorber,non-crystallizing ionic liquids (ILs), and highly efficient solutionheat exchangers. In some embodiments, the absorber 202 can comprise anopen or semi-open membrane-based absorber. Open absorbers arefundamentally different than closed absorbers. Without wishing to bebound by any particular theory, the presence of air in an open absorbersystem may lead to an order of magnitude lower absorption rate whencompared to a closed absorber. In some embodiments, to overcome thisdisadvantage of the open absorber system, the absorber surface area canbe drastically increased. To provide a high surface area, designs havegravitated towards packed bed adiabatic absorbers, in which air anddesiccant flows are given a large interfacial area to interact. The heatof phase change is not immediately removed, requiring that the desiccantflows at substantially higher flow rates, leading to a decline in thecoefficient of performance (COP). In contrast, an internally cooledabsorber can operate at an order of magnitude lower flow rate than itsopen, adiabatic counterparts, but requires a more complex design asthree different fluids: air; absorbent; and a cooling medium areinvolved. Thus, the semi-open systems described herein are advantageousbecause they do not experience all of the disadvantages of fully openabsorption and/or desorption systems, while at the same time allowingfor a less segmented, more integrated system in which efficiencies inheat exchange and reuse of process streams is possible.

In some embodiments, an absorber can include polymer materials (e.g.,for desiccant or water contact surfaces) or be constructed substantiallyor exclusively of polymers. Metals can be used in conjunction withpolymers, although the effects of corrosion should be considered in thechoice of a metal and the mode of construction as a semi-open system mayexpose the materials of construction to water, carbon dioxide, oxygen,and other potential corrosives.

FIGS. 4A and 4B show a heat pump water heater (FIG. 4A) and acorresponding energy efficient, cost-effective separate sensible andlatent cooling (SSLC) HVAC system implemented as a double-effectabsorption cycle (FIG. 4b ) for residential use. The system of FIG. 4Bmay provide approximately a 2.5 times energy efficiency at residentialuse scale increase compared to conventional liquid desiccantdehumidification and cooling systems at the same scale. This representsthe first time an efficient and cost-effective implementation of theseparate handling of sensible and latent loads, for example, atresidential scale.

As shown in FIG. 4B, the air is first dehumidified (latent cooling) asit passes through the absorber 202. The condensate is then used tosensibly cool the air, through the use of an indirect evaporative cooler210 (condensate is not returned to the process air stream). This resultsin the net decrease in the relative humidity and temperature of theprocess air stream. This ability to separately handle sensible andlatent loads enables control of indoor humidity levels, improving IAQ.As an HFC-free, heat driven system, it provides for the reduction inpeak electrical power consumption, and effectively resolves the use ofglobal warming refrigerants in the HVAC industry.

It order to implement this technology, it may be advantageous or evenrequired to use compact, efficient heat and mass exchangers 206, 208(HMX 206, 208) for the desorbers 212, 214. According to someembodiments, a single-effect desorber 211 may be used for the waterheating application (FIG. 4A) and a double-effect desorber 212, 214 maybe used for the HVAC application (FIG. 4B). Although the desorberarchitecture is different for these two applications, the upper desorberin the double-effect cycle is similar with respect to flow types/ratesto the single-effect desorber with the exception that, according to someembodiments, it functions at a higher temperature (about 200° C.) thanthe single-effect desorber (about 130° C.).

In some embodiments, the hot side module design can include anintegrated desorbing, condensing surface, and a condensing heatexchanger. A vapor permeable membrane can be installed between thedesorber and condenser sections to prevent the desiccant solution fromexiting the desorber. To enhance the desorption rate, the desorbingsurface can use a copper finned structure. In some embodiments, thisfinned structure can be brazed to the stainless-steel surface and nickelplated for corrosion prevention. The two sides, desorbing andcondensing, can be bolted together with a gasket material to permit themodule's disassembly if necessary during system testing. The desorbingsurface can then be heated by hot oil. In some embodiments, thedesorbing and condensing surfaces can be between about 0.1 m² and about0.2 m², about 0.11 m² to about 0.15 m², or about 0.12 m² to about 0.13m², inclusive of all values and ranges therebetween. In someembodiments, the desorbing and condensing surface can be about 0.122 m²and about 0.128 m², respectively. The interior dimensions(Height×Width×Depth) of the module can be between about 0.3 m×about 0.2m×about 0.025 m and about 0.6 m×about 0.4 m×about 0.1 m, between about0.35 m×about 0.25 m×about 0.05 m and about 0.5 m×about 0.35 m×about0.075 m, or the like. In some embodiments, the interior dimensions(Height×Width×Depth) can be about 0.461 m×about 0.311 m×about 0.061 m.In some embodiments, the desorber portion of the module can have athickness/depth of between about 0.01 m and about 1 m, about 0.015 m andabout 0.9 m, about 0.02 m and about 0.8 m, about 0.025 m and about 0.7m, about 0.03 m and about 0.6 m, about 0.01 m and about 0.9 m, about0.01 m and about 0.8 m, about 0.01 m and about 0.7 m, about 0.01 m andabout 0.6 m, about 0.01 m and about 0.5 m, about 0.01 m and about 0.4 m,about 0.01 m and about 0.3 m, about 0.01 m and about 0.2 m, about 0.2 mand about 1 m, about 0.3 m and about 1 m, about 0.4 m and about 1 m,about 0.5 m and about 1 m, about 0.6 m and about 1 m, about 0.7 m andabout 1 m, about 0.8 m and about 1 m, or about 0.9 m and about 1 m,inclusive of all values and ranges therebetween. In some embodiments,the desorber portion of the module can have a thickness/depth of lessthan about 1 m, about 0.9 m, about 0.8 m, about 0.7 m, about 0.6 m,about 0.5 m, about 0.4 m, about 0.3 m, about 0.2 m, about 0.1 m, about0.09 m, about 0.08 m, about 0.07 m, about 0.06 m, about 0.05 m, about0.04 m, about 0.03 m, about 0.02 m, or about 0.01 m, inclusive of allvalues and ranges therebetween. In some embodiments, the desorberportion of the module can have a thickness/depth of greater than about0.01 m, about 0.02 m, about 0.03 m, about 0.04 m, about 0.05 m, about0.06 m, about 0.07 m, about 0.08 m, about 0.09 m, about 0.1 m, about 0.2m, about 0.3 m, about 0.4 m, about 0.5 m, about 0.6 m, about 0.7 m,about 0.8 m, about 0.9 m, or about 1 m, inclusive of all values andranges therebetween. In some embodiments, the desorber portion of themodule can have a thickness/depth of about 0.034 m.

In other embodiments, the physical size of the desorber design can bereduced through the implementation of a multiple-plate design where thecapacity is scalable through the addition of plates. In someembodiments, the design can include only an upper desorber or a lowerdesorber, while in other embodiments the design can include both anupper desorber and a lower desorber.

FIGS. 5A-5D show an absorber 302 that can be used in an LDDS (e.g., LDDS10 or LDDS 20) and the results of using various surface treatment andbonding techniques. In some embodiments, a desiccant solution 334 can becaused to flow (e.g., as a thin film, as discrete droplets, as acontinuous flow, in discrete batches, or the like) on one or both sidesof a cooling medium conduit 334 while constrained by a membrane 336(e.g., a superhydrophobic membrane), as shown in FIG. 5A, such thatprocess air 332 can flow past the desiccant solution 334, which cancause the absorption of water vapor from the process air 332 into thedesiccant solution 334. The absorber of FIGS. 5A-5D can be modular,permitting plates 338 to be stacked, as shown in FIG. 5B to achieve adesired capacity. In some embodiments, the surface of the polymer can behydrophilic, which, in conjunction with the surface structures, mayresult in spreading the desiccant solution as a thin film over some orall of the plates 338, as shown in FIG. 5C, unlike that of a hydrophobicsurface, where in the absence of these features, the desiccant solution334 may form channels across the surface of the plate 338 rather thanspreading over a greater portion or substantially all of the surface ofthe plate 338 when flowing down, up, or across the plate 338. In someembodiments, the membrane 336 can be bonded over the surface structuresand edge structures. FIG. 5D shows one module from the absorber 302comprising the plates 338. The plastic for an all plastic absorber 302,according to some embodiments, can be polycarbonate, polyacrylates,polyesters, polyimides, combinations thereof, or any other polymermaterials. The surface of the polymer can be rendered hydrophilic bycoating, inducing a surface reaction, disposing or defining surfacefeatures, or any other method suitable to form a hydrophilic surface ofthe polymer. The heat exchanging plates 338 for the flow of thedesiccant solution 334 (e.g., a working IL solution) can be decoratedwith an array of fins, e.g., a staggered array of rectangular fins, thatmay affect the flow pattern and resulting contact area between the fluidand the cooling surface, the substrate. A rivulet flow regime isexhibited by liquids falling over a flat vertical surface, as in thecase of conventional heat exchanging plates. In contrast, the fins mayallow the flow to be transformed into the continuous film regime whenthe wall is decorated with surface features, for example, as shown inbox A of FIG. 5D. The absorber 302 can have an array of structuresoptimized to yield desired flow characteristics. In some embodiments,the fin elements of the array can be located sufficiently close to eachother such that the desired flow effect is achieved but sufficiently farfrom each other to ensure that capillary forces do not dominate theflow. In other words, texture on the surface of a plate 338 can helpincrease flow continuity, but if surface features are positionedsufficiently close together such that the interstitial regionstherebetween exert capillary forces on the desiccant solution, then atleast some of the desiccant solution will become impregnated within theinterstitial regions, resulting in discontinuous flow. In someembodiments, plate 338 surface decorations other than a staggered arrayof rectangular fins can be used.

In some embodiments, the water vapor can pass through the membrane 336(e.g., a nanostructured membrane) and condense over a fin decoratedsurface of the plate 338, which can be cooled by the system's coolant.The membrane need not be porous if the nature of the material allows fora sufficiently rapid diffusion through the material under the normalconditions of use. For instance, the membrane may be one that remainssaturated in the water, yet allows for active diffusion to the desiccantsolution (e.g., working IL solution). The membrane 336 can be comprisedof fibrous polymers. Polymers that can be used include polyamides,polyethers, polyimides, polyesters or other polymers that interact withbut do not dissolve in water. The membrane 336 can provide a surfacethat is extremely porous to allow rapid water exchange over a roughmembrane that has a very high area surface.

In some embodiments, the desiccant solution can comprise one or moreILs, which exhibit favorable crystallization and corrosioncharacteristics with regard to the LDDS 10, the LDDS 20, and othersystems and apparatuses described herein. Conventional absorbents, suchas lithium bromide, lithium chloride, calcium chloride and similarbrines, often can be used in only limited operating parameter ranges,such as a narrow range of temperature, pressure, and the like, mainlydue to crystallization of the same during use, which requires controlequipment to monitor and rapidly/constantly adjust the system workingconditions to avoid crystallization of such absorbents, even in case ofpower outages. The prohibitively high cost of such control systems andthe monitoring and dynamic process control systems necessary for suchconventional systems and absorbents can make their implementation formany applications and conditions impossible, e.g., for small scalessystems.

FIGS. 6A-6D show a desorber 312 that can be used in an LDDS (e.g., LDDS10 or LDDS 20). In some embodiments, the desorber 312 can be configuredto heat the dilute solution in order to cause a phase change of water inthe dilute solution to water vapor that can be desorbed. In someembodiments, the first desorber 312 can include a plurality ofdesorption plates configured to facilitate desorption when the watervapor and desiccant solution comes into contact with the plates,increasing the concentration of desiccant in the dilute solution to forman intermediate solution. In some embodiments, the heat ofdesorption/condensation can be captured by a heat exchanger. In someembodiments, at least a portion of the intermediate solution can then becommunicated to a second desorber 314 such that at least a portion ofthe remaining water in the intermediate solution is desorbed, forming aconcentrated solution. In some embodiments, the heat ofdesorption/condensation at the desorber 312 can be used to heat theintermediate solution for regeneration at the second desorber 314. Oncethe concentrated solution is formed at the second desorber 312, it hasbeen fully or substantially fully regenerated for subsequent desiccationpurposes by an absorber (e.g., absorber 102, 202, 302). The desorbedwater vapor from the second desorber 312 can be communicated to acondenser such that the water vapor can be condensed to make-up water,can be used to heat various processes and streams elsewhere in theprocess, and/or can be disposed to waste.

As illustrated in FIGS. 6A-6D, the desorber 312 can include a firsthousing portion 312 a dimensioned and configured to be removably coupledto a second housing portion 312 b to form a housing of the desorber 312.In some embodiments, the desorber 312 can include a plurality ofapertures through at least one of the first housing portion 312 a or thesecond housing portion 312 b, the plurality of apertures defining aplurality of inlet and outlet ports for process streams, e.g., thedesiccant solution, the water vapor, the water, and/or a heat exchangemedium (oil). In some embodiments, a first solution inlet port 313 a anda first solution outlet port 313 b can be defined by apertures throughthe housing portion 312 a, e.g., at a top of the desorber 312 and at abottom of the desorber 312, respectively. In some embodiments, a vaporoutlet port 313 c can be defined by an aperture through the firsthousing portion 312 a of the desorber 312, e.g., at or near the top ofthe desorber 312. In some embodiments, a water outlet port 313 d can bedefined by an aperture through the first housing portion 312 a of thedesorber 312, e.g., at or near the bottom of the desorber 312. In someembodiments, a second solution inlet port 313 e can be defined by anaperture in the second housing portion 312 b of the desorber 312, e.g.,positioned at or near the top of the desorber 312. In some embodiments,a second solution outlet port 313 f can be defined by an aperturethrough the second housing portion 312 b of the desorber 312, e.g., ator near the bottom of the desorber 312. In some embodiments, a heatexchange medium (oil) inlet port 313 g can be defined by an aperturethrough the second housing portion 312 b of the desorber 312, e.g.,positioned at or near the bottom of the desorber 312. In someembodiments, a heat exchange medium (oil) outlet port 313 h can bedefined by an aperture through the second housing portion 312 b of thedesorber 312, e.g., positioned at or near the top of the desorber 312.

In some embodiments, two or more of the apertures can define, at leastin part, a fluid flow path through the desorber 312. In someembodiments, a fluid flow path can be defined between the first solutioninlet port 313 a and the first solution outlet port 313 b and caninclude a plurality of desorption plates/diffusion plates stacked in aninner volume of the first housing portion 312 a of the desorber 312. Insome embodiments, a fluid flow path can be defined between the firstsolution inlet port 313 a and the vapor and water outlet port 313 c and313 d in which a volume of water in the dilute desiccant solution ischarged into the desorber 312 through the first solution inlet port 313a, a portion of the volume of water desorbs/diffuses out of the dilutedesiccant solution, a first sub-portion of the portion of the volume ofwater exits the desorber 312 through the vapor outlet port 313 c, and asecond sub-portion of the portion of the volume of water exits thedesorber 312 through the water outlet port 313 d. Other fluid flow pathscan include between the heat exchange medium inlet port 313 g and theheat exchange medium outlet port 313 h.

In some embodiments, the first housing portion 312 a and/or the secondhousing portion 312 b can at least partially define an inner volume 312x configured to contain or partially contain a first plurality of plates312 c and/or a second plurality of plates 312 d. In some embodiments,the shell can include or be formed from any suitably durable materialwithout limitation. In some embodiments, the plurality of plates can bestacked or joined together and disposed within the inner volume 312 x ofthe shell of the desorber 312. In some embodiments, a separator plate312 e can be disposed between the two stacks of plates 312 c, 312 d. Insome embodiments, a dilute solution comprising desiccant and water canbe communicated into the desorber 312 through the first solution inletport 313 a, along a solution flow path through the desorber 312, and outthe first solution outlet port 313 b.

In some embodiments, a heat exchange medium can be communicated into theheat exchange medium inlet port 313 g, through a heat exchange mediumflow path through the desorber 312, and out the heat exchange mediumoutlet port 313 h. In some embodiments, communicating the heat exchangemedium through the desorber 312 can heat the desiccant solutioncomprising desiccant and water such that the water in solution isconverted to water vapor and is communicated out of the desorber 312 viathe water vapor outlet port. In some embodiments, the desiccant solutioncan heat the heat exchange medium in the desorber 312 such that the heatexchange medium leaving the desorber 312 can exchange heat elsewhere inthe process. In some embodiments, the desorber 312 can be configuredsuch that the heat exchange medium and the desiccant solution comprisingdesiccant and water are fluidically isolated each from the other. Insome embodiments, the desorber 312 can be configured such that the heatexchange medium is communicated along a heat exchange medium flow paththrough the stacked plates 312 c on a second side of the separator plate312 e while the desiccant solution comprising desiccant and water iscommunicated along a desiccant solution flow path through the stackedplates on a first side of the separator 312 e. Design fluidtemperatures, according to one embodiment, are provided in Table 1.

Without wishing to be bound by any particular theory, a key factor thatmay limit the operation and application of existing LiBr systems is theneed for cooling the absorber using a wet cooling tower or anothercooling cycle. The need for a wet cooling tower has limited the use ofLiBr systems to large scales. Development efforts have been primarilyfocused on building larger heat exchangers, hybridization with vaporcompression cycles, and to some extent using additives to delay LiBrcrystallization. The fundamental physical barrier in building anair-cooled LiBr system is that the high vapor pressure of the LiBrsolution at temperatures in excess of 30° C. inhibits water vaporabsorption from the evaporator in a closed cycle or the humid air in anopen cycle. FIG. 7 compares the vapor pressure of four ILs, where IL-Ais Evonik CrysCo Plus 2200, IL-B is Evonik CrysCo Plus 2630, IL-C ispiSorb 275, and IL-E is Sorbionic4 with that of the LiBr solution. Asignificant vapor pressure depression is observed in the case of IL-A.The vapor pressure of IL-A at 50° C. is approximately equal to that ofthe LiBr solution at 30° C.

TABLE 1 Multi-plate Desorber Fluid Temperatures Double-EffectConfiguration Upper Desorber Hot Side (Oil) Cold Side (IL) Vapor InletTemperature (° C.) 180 140 NA Outlet Temperature (° C.) 165 160 145 HotSide Lower Desorber (Vapor*) Cold Side (IL) Vapor Inlet Temperature (°C.) 145 74 NA Outlet Temperature (° C.) 45 80 75 Single-EffectConfiguration Hot Side (Oil) Cold Side (IL) Vapor Inlet Temperature (°C.) 155 98 NA Outlet Temperature (° C.) 146 120 120 *Note: Fluid entersas vapor from upper desorber and exits as condensate.

This extra temperature window enables air-cooling of the absorber in hotclimates. In some embodiments, the IL can include one or more of EvonikCrysCo Plus 2200, Evonik CrysCo Plus 2630, piSorb 275, and Sorbionic4,1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide,1-ethyl-3-methylimidazolium bis (trifluoromethyl-sulfonyl)amide,tetra-nbutylphosphonium trifluoromethanesulfonyl leucine,N-alkyl-N,N-dimethylhydroxyethylammoniumbis(trifluoromethane)sulfonylimidelithium bromide, lithium chloride, calcium chloride,combinations thereof, or the like. In some embodiments, the IL caninclude one or more of 1-butyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)amide, tetra-nbutylphosphoniumtrifluoromethanesulfonyl leucine,N-alkyl-N,N-dimethylhydroxyethylammoniumbis(trifluoromethane)sulfonylimide, combinations thereof, or the like. Regardless of thespecific IL used, the value of a non-crystallizable desiccant includesmany of the specific benefits outlined herein.

Solution heat exchangers substantially impact the cycle's COP becausethey are responsible for recovery of the heat added to the desiccant inthe desorber. To deal with a higher viscosity displayed by IL solutions,the flow cross-section is increased, where proper choice of thegeometrical parameters, such as width, length, number of flow paths, andflow cross-section area, and proper choice of the flow rate andtemperature, an effectiveness of more than 0.95 can be achieved withcompact low-cost plate-and-frame heat exchanger, as shown in FIG. 8.

The system's operating conditions are constructed to address the median1% design air temperature of 32° C. for the US. In some embodiments, forexample when the desiccant solution comprises IL-C, this may necessitateoperation of the condenser at about 45° C. to provide sufficient thermalpotential to reject heat to air even at high ambient temperatures. Toprovide the ability to regenerate IL-C such that it produces thecondenser saturation vapor temperature of 45° C., the lower desorbersolution exit concentration and temperature are 97% and 84° C.,respectively. The upper desorber exit concentration and temperature are92% and 160° C., respectively. These operating conditions result in thedesiccant solution entering the absorber at a concentration andtemperature of 97% and 28° C., respectively. This corresponds to a vaporpressure of 0.28 kPa, providing substantially greater absorption(dehumidification) potential than LiBr or LiCl at similar operatingconditions. These data, related to the process state points presented onFIG. 3 for the complete system and in FIG. 9 for the absorber-doubledesorber portion of the system, are provided in Table 2 and reproducedin FIG. 9. Element numbering from FIG. 3 is re-created in FIG. 9 toidentify the elements of the LDDS system of FIG. 9, however this is notintended to define or limit the operational parameters, configuration,or process steps to those described above with respect to the LDDS 20 inFIG. 3.

TABLE 2 System Operational Parameters. Temp Vapor Pres. Conc. Point (°C.) (kPa) (%) 1 160  96 92 2 84 9.5 97 3 28 0.28 97 4  45* 9.5 — *Note:Vapor Saturation Temperature

For at least some of the embodiments described herein and embodimentsnot explicitly included herein but understood by one of skill in the artto be included in the scope of the claimed invention, the double-effectconfiguration provides nearly twice the efficiency of a single-effectsystem. In some embodiments, the system is further enhanced inefficiency by physical separation of the desorber and condenser heatexchangers. In some configurations and embodiments, ambient air can beintroduced into a plastic steam-air heat exchanger and the desiccantsolution can be regenerated in an extremely compact steam-solution heatexchanger. This regeneration approach results in a latent effectivenessapproaching 100% and an estimated cycle COP of about 1.8 based on theamount of latent heat it handles and the heat input. Approximatingparasitic losses of about 5% and a gas burner efficiency of about 87%, aprimary COP of about 1.5 is calculated for the system. The applicationof these systems for DOAS, desiccant-based cooling, and handling latentheat loads in buildings, has the potential to provide significant energysavings.

FIG. 10 illustrates a high desorber 412 for a double-effect systemcomprising a low desorber and the high desorber 412, e.g., correspondinggenerally in function to the second desorber 214 and the first desorber212, respectively. The high desorber 412 can include a heat input (notshown), for example but not limited to, using heating oil, to transferheat to the desiccant solution. The low desorber can use the condensingwater vapor to transfer heat to a desiccant solution (e.g., desiccantsolution 334). As shown in FIG. 10, the high desorber is configured suchthat the desiccant solution (e.g., desiccant solution 334) can betransported across a fin decorated surface of the plate (e.g., plate338), the fin decoration characteristics, surface chemistry, and otherparameters configured to maximize a desorption rate of water from theprocess air (e.g., 332) into the desiccant solution. As shown in FIG.10, the high desorber 412 can be configured such that the oil flowing ona back surface of the plate opposite the desiccant solution on the findecorated surface. The desorbed water vapor is directed to the lowerdesorber where it condenses and transfers its latent heat to thedesiccant solution.

In some embodiments, a high desorber 412 and a low desorber 414 can beconfigured, as shown in FIG. 10, such that the desiccant solution (e.g.,a working IL solution) is heated by an external heat source 440 for thehigh desorber 412 and is transmitted through a heat exchanger SHX1,e.g., a high heat exchanger, where the hot concentrated desiccantsolution (working solution) from the high desorber 412 transfers heat tothe dilute desiccant solution feeding the high desorber 412. Thedesorbed vapor driven from the concentrated desiccant solution (workingsolution) in the high desorber 412 condenses in a condenser in the lowerdesorber 414 to transfer its heat of condensation to the concentrateddesiccant solution from the high desorber 412 in the low desorber 414for further concentration of the concentrated desiccant solution withthe condensed water from the lower desorber 414 exiting the system.

Although illustrated in FIG. 11 such that the high desorber 412 issituated above the low desorber 414, this is not required, as isillustrated in FIGS. 12 and 13, where the high desorber 512, 612 and lowdesorber 514, 614 are adjacent to each other, differing in the manner inwhich the high desorber 512, 612 is connected to the low desorber 514,614. In some embodiments, a conduit can be employed to deliver thedesorbed water vapor to the condenser of the lower desorber 514, asillustrated in FIG. 12. In some embodiments, the high desorber 612 andlow desorber 614 can effectively be combined into a single unit wherethe desorbed vapor from the high desorber portion 612 is directlydelivered to the condenser of the low desorber portion 614, asillustrated in FIG. 13. A pump 542, 642 is shown beyond the concentrateddesiccant solution of the high heat exchanger SHX1, but this pump may besituated elsewhere in the system with respect to the high desorber 512,612 and the low desorber 514, 614. Alternatively the pump 542, 642 canbe a redundant pump in terms of the transport of the concentrateddesiccant solution.

In some embodiments, for example for many of the dual-desorberconfigurations, the concentrated desiccant solution transported from thelow desorber can be passed through a second heat exchanger SHX2, a lowheat exchanger, where heat is transferred from the more concentrateddesiccant solution for subsequent entry to an absorber (e.g., 102, 202,302). In the absorber, ambient air in communication with the desiccantsolution transfers water vapor and heat to the more concentrateddesiccant solution (working solution) to form a dilute desiccantsolution and a cooling fluid, generally water, can be used to remove aportion of the heat from the dilute desiccant solution. Depending uponambient temperatures and the most economical way to provide coolingwater, the absorber 702 can be configured as in any of FIG. 14, 15, or16, where the cooling water is:

within a closed loop that is externally cooled in a radiator 744external to the system and the water vapor and condensate from the lowdesorber 714 is vented to ambient, as shown in FIG. 14;

evaporated by the heat of dilution of the concentrated desiccantsolution (working solution) in the absorber 802 and transferred to acondenser unit where it is combined with the water vapor and watercondensate from the low desorber 814, as shown in FIG. 15; or

where water vapor generated by evaporation of the cooling fluid passedthrough the second heat exchanger SHX2 to further heat the water vaporfrom the absorber 902 and transferred the warmed water vapor to acondenser unit where it is combined with the water vapor and watercondensate from the low desorber 914, as shown in FIG. 16.

It should be understood that the examples and embodiments describedherein are for illustrative purposes only and that various modificationsor changes in light thereof will be suggested to persons skilled in theart and are to be included within the spirit and purview of thisapplication.

In order to address various issues and advance the art, the entirety ofthis application (including the Title, Headings, Background, Summary,Brief Description of the Drawings, Detailed Description, Abstract,Figures, any Appendices, and otherwise) shows, by way of illustration,various embodiments in which the disclosed innovations may be practiced.The advantages and features of the application are of a representativesample of embodiments only, and are not exhaustive and/or exclusive.They are presented to assist in understanding and teach the disclosedprinciples.

It should be understood that they are not representative of alldisclosed innovations. As such, certain aspects of the disclosure havenot been discussed herein. That alternate embodiments may not have beenpresented for a specific portion of the innovations or that furtherundescribed alternate embodiments may be available for a portion is notto be considered a disclaimer of those alternate embodiments. It will beappreciated that many of those undescribed embodiments incorporate thesame principles of the innovations and others are equivalent. Thus, itis to be understood that other embodiments may be utilized andfunctional, logical, operational, organizational, structural and/ortopological modifications may be made without departing from the scopeand/or spirit of the disclosure. As such, all examples and/orembodiments are deemed to be non-limiting throughout this disclosure.

Also, no inference should be drawn regarding those embodiments discussedherein relative to those not discussed herein other than it is as suchfor purposes of reducing space and repetition. For instance, it is to beunderstood that the logical and/or topological structure of anycombination of any program components (a component collection), othercomponents and/or any present feature sets as described in the figuresand/or throughout are not limited to a fixed operating order and/orarrangement, but rather, any disclosed order is exemplary and allequivalents, regardless of order, are contemplated by the disclosure.

Various inventive concepts may be embodied as one or more methods,systems, apparatuses, and/or kits, of which at least one example hasbeen provided. The acts performed as part of the method may be orderedin any suitable way. The configuration and ordering of constituent partsof a system or apparatus as described may be changed and/or wholeconstituent parts may be removed, according to any suitable manner inwhich the system or apparatus can be comprised. Accordingly, embodimentsmay be constructed in which acts are performed in an order differentthan illustrated, which may include performing some acts simultaneously,even though shown as sequential acts in illustrative embodiments. Putdifferently, it is to be understood that such features may notnecessarily be limited to a particular order of execution, but rather,any number of threads, processes, services, servers, and/or the likethat may execute serially, asynchronously, concurrently, in parallel,simultaneously, synchronously, and/or the like in a manner consistentwith the disclosure. As such, some of these features may be mutuallycontradictory, in that they cannot be simultaneously present in a singleembodiment. Similarly, some features are applicable to one aspect of theinnovations, and inapplicable to others.

In addition, the disclosure may include other innovations. Applicantreserves all rights in any and all innovations including the right toclaim such innovations, file additional applications, nonprovisionalapplications, design applications, continuations, continuations-in-part,divisionals, and/or the like thereof. As such, it should be understoodthat advantages, embodiments, examples, functional, features, logical,operational, organizational, structural, topological, and/or otheraspects of the disclosure are not to be considered limitations on thedisclosure as defined by the embodiments, claims or limitations onequivalents to the embodiments and/or claims. Depending on theparticular desires and/or characteristics of an individual and/orenterprise user, database configuration and/or relational model, datatype, data transmission and/or network framework, syntax structure,and/or the like, various embodiments of the technology disclosed hereinmay be implemented in a manner that enables a great deal of flexibilityand customization as described herein.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein, unless clearlyindicated to the contrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein, should be understood to mean“either or both” of the elements so conjoined, i.e., elements that areconjunctively present in some cases and disjunctively present in othercases. Multiple elements listed with “and/or” should be construed in thesame fashion, i.e., “one or more” of the elements so conjoined. Otherelements may optionally be present other than the elements specificallyidentified by the “and/or” clause, whether related or unrelated to thoseelements specifically identified. Thus, as a non-limiting example, areference to “A and/or B”, when used in conjunction with open-endedlanguage such as “comprising” can refer, in one embodiment, to A only(optionally including elements other than B); in another embodiment, toB only (optionally including elements other than A); in yet anotherembodiment, to both A and B (optionally including other elements); etc.

As used herein, “or” should be understood to have the same meaning as“and/or” as defined above. For example, when separating items in a list,“or” or “and/or” shall be interpreted as being inclusive, i.e., theinclusion of at least one, but also including more than one, of a numberor list of elements, and, optionally, additional unlisted items. Onlyterms clearly indicated to the contrary, such as “only one of” or“exactly one of,” or, when used in claims, “consisting of,” will referto the inclusion of exactly one element of a number or list of elements.In general, the term “or” as used herein shall only be interpreted asindicating exclusive alternatives (i.e. “one or the other but not both”)when preceded by terms of exclusivity, such as “either,” “one of,” “onlyone of,” or “exactly one of.” “Consisting essentially of,” when used inclaims, shall have its ordinary meaning as used in the field of patentlaw.

As used herein, the phrase “at least one,” in reference to a list of oneor more elements, should be understood to mean at least one elementselected from any one or more of the elements in the list of elements,but not necessarily including at least one of each and every elementspecifically listed within the list of elements and not excluding anycombinations of elements in the list of elements. This definition alsoallows that elements may optionally be present other than the elementsspecifically identified within the list of elements to which the phrase“at least one” refers, whether related or unrelated to those elementsspecifically identified. Thus, as a non-limiting example, “at least oneof A and B” (or, equivalently, “at least one of A or B,” or,equivalently “at least one of A and/or B”) can refer, in one embodiment,to at least one, optionally including more than one, A, with no Bpresent (and optionally including elements other than B); in anotherembodiment, to at least one, optionally including more than one, B, withno A present (and optionally including elements other than A); in yetanother embodiment, to at least one, optionally including more than one,A, and at least one, optionally including more than one, B (andoptionally including other elements); etc.

Unless otherwise indicated, all numbers expressing quantities ofequipment, operating conditions, and so forth used in the specificationand claims are to be understood as being modified in all instances bythe term “about”. Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the present specification and attachedclaims are approximations that can vary depending upon the desiredproperties sought to be obtained by the present application. Generallythe term “about”, as used herein when referring to a measurable valuesuch as an amount of weight, time, temperature, etc. is meant toencompass ±10% of the stated value. For example, a value of “1,000”,which would be construed from above as meaning “about 1,000”, indicatesa range of values from 900 to 1,100, inclusive of all values and rangestherebetween.

All transitional phrases such as “comprising,” “including,” “carrying,”“having,” “containing,” “involving,” “holding,” “composed of,” and thelike are to be understood to be open-ended, i.e., to mean including butnot limited to. Only the transitional phrases “consisting of” and“consisting essentially of” shall be closed or semi-closed transitionalphrases, respectively, as set forth in the United States Patent OfficeManual of Patent Examining Procedures, Section 2111.03.

All examples and/or embodiments are deemed to be non-limiting throughoutthis disclosure. Also, no inference should be drawn regarding thoseembodiments discussed herein relative to those not discussed hereinother than it is as such for purposes of reducing space and repetition.For instance, it is to be understood that the logical and/or topologicalstructure of any combination of any data flow sequence(s), programcomponents (a component collection), other components and/or any presentfeature sets as described in the figures and/or throughout are notlimited to a fixed operating order and/or arrangement, but rather, anydisclosed order is exemplary and all equivalents, regardless of order,are contemplated by the disclosure. Furthermore, it is to be understoodthat such features are not limited to serial execution, but rather, anynumber of threads, processes, processors, services, servers, and/or thelike that may execute asynchronously, concurrently, in parallel,simultaneously, synchronously, and/or the like are also contemplated bythe disclosure. As such, some of these features may be mutuallycontradictory, in that they cannot be simultaneously present in a singleembodiment. Similarly, some features are applicable to one aspect of theinnovations, and inapplicable to others. In addition, the disclosureincludes other innovations that are disclosed and may not explicitlyrecited. As such, it should be understood that advantages, embodiments,examples, functional, features, logical, operational, organizational,structural, topological, and/or other aspects of the disclosure are notto be considered limitations on the disclosure as defined by theembodiments, examples, claims or limitations on equivalents to theembodiments, examples, and/or claims.

What is claimed is:
 1. A desorber configured to desorb water from aheated working solution comprising a desiccant and water vapor, thedesorber comprising: a desorber housing comprising a first housingportion and a second housing portion, the first housing portion at leastpartially defining a first portion of an inner volume of the desorberhousing and the second housing portion at least partially defining asecond portion of the inner volume of the desorber housing; a firstplurality of diffusion plates disposed within the first portion of theinner volume of the desorber housing, the first plurality of diffusionplates defining a first one or more apertures therethrough; and a secondplurality of diffusion plates disposed within the second portion of theinner volume of the desorber housing, the second plurality of diffusionplates defining a second one or more apertures therethrough, wherein thefirst one or more apertures are dimensioned and configured such thatwater vapor is directly desorbed through the first one or more aperturesat a temperature of between about a boiling point temperature of waterand about the boiling point temperature of the desiccant, and thedesorber being configured to directly desorb at least a portion of thewater vapor from the working solution in a still air environment.
 2. Thedesorber of claim 1, wherein the first housing portion defines a firstworking solution inlet port, a vapor outlet port, a water outlet port,and a first working solution outlet port, and wherein the second housingportion defining a second working solution inlet port, a heat exchangefluid inlet port, a heat exchange fluid outlet port, and a secondworking solution outlet port.
 3. The desorber of claim 1, wherein eachdiffusion plate of the first plurality of diffusion plates issubstantially rectangular in shape, each diffusion plate comprising: afirst aperture offset in a radial direction from a radial axis of eachdiffusion plate of the first plurality of diffusion plates; and a secondaperture offset in an opposite radial direction from the radial axis ofeach diffusion plate of the first plurality of diffusion plates, thesecond aperture defined parallel to the first aperture and having thesame dimensions.
 4. The desorber of claim 3, wherein the first pluralityof diffusion plates are stacked together to form a first diffusion platestack, the first diffusion plate stack at least partially defining afirst fluid flow path through the first housing portion of the desorberhousing, and wherein the first aperture and the second aperture areconfigured to reduce the first fluid flow path such that water vapordiffuses more rapidly through the first diffusion plate stack.
 5. Thedesorber of claim 4, wherein each diffusion plate of the secondplurality of diffusion plates is substantially rectangular in shape,each diffusion plate of the second plurality of diffusion platescomprising: a third aperture defined linearly through each plate of thesecond plurality of diffusion plates in an axial direction and centeredradially.
 6. The desorber of claim 5, wherein the second plurality ofdiffusion plates are stacked together to form a second diffusion platestack, the second diffusion plate stack at least partially defining asecond fluid flow path through the second housing portion of thedesorber housing greater than the first fluid flow path through thefirst housing portion of the desorber housing, and wherein the seconddiffusion plate stack is configured to exchange thermal energy with aheat exchange fluid.
 7. The desorber of claim 1, wherein the workingsolution comprises an ionic liquid (IL) and water.
 8. The desorber ofclaim 1, wherein the IL is non-crystalizable.
 9. The desorber of claim1, wherein the IL comprises 1-butyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazoliumbis(trifluoromethyl-sulfonyl)amide, tetra-nbutylphosphoniumtrifluoromethanesulfonyl leucine, orN-alkyl-N,N-dimethylhydroxyethylammoniumbis(trifluoromethane)sulfonylimide.
 10. A method for increasing a concentration of thedesiccant in the working solution and cooling the working solution usingthe desorber of claim 1, the method comprising: charging the heatedworking solution into the first portion of the inner volume of thedesorber housing; communicating the heated working solution along thefirst fluid flow path such that at least a first portion of water vapordesorbs from the heated working solution and is communicated out of thedesorber, forming a concentrated working solution; communicating theconcentrated working solution from the first portion of the inner volumeof the desorber housing into the second portion of the inner volume ofthe desorber housing; and communicating the first concentrated workingsolution along the second fluid flow path such that the heat exchangefluid removes heat from the concentrated working solution.
 11. Anabsorber plate configured to absorb water from a process air, theabsorber plate comprising: a central channel having a first surface anda second surface; a first desiccant solution channel having a firstsurface and a second surface and configured to communicate a firstportion of the desiccant solution therethrough, the first surface of thefirst desiccant solution channel coupled to the first surface of thecentral channel; a first membrane having a first surface and a secondsurface, the second surface of the first membrane fluidically coupled tothe desiccant solution channel, the first surface of the first membraneand the first portion of the desiccant solution configured to absorbwater vapor from process air nearby the first membrane; a seconddesiccant solution channel having a first surface and a second surfaceand configured to communicate a second portion of the desiccant solutiontherethrough, the first surface of the second desiccant solution channelcoupled to the second surface of the central channel; a second membranehaving a first surface and a second surface, the second surface of thesecond membrane fluidically coupled to the desiccant solution channel,the first surface of the second membrane and the second portion of thedesiccant solution configured to absorb water vapor from process airnearby the second membrane.
 12. The absorber plate of claim 11, whereinthe desiccant solution comprises an ionic liquid (IL).
 13. The absorberof claim 12, wherein the IL is non-crystalizable.
 14. The absorber ofclaim 12, wherein the IL comprises 1-butyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazoliumbis(trifluoromethyl-sulfonyl)amide, tetra-nbutylphosphoniumtrifluoromethanesulfonyl leucine, orN-alkyl-N,N-dimethylhydroxyethylammoniumbis(trifluoromethane)sulfonylimide.
 15. The absorber of claim 11, wherein the central channelis a heat exchange channel configured to communicate a heat exchangefluid therethrough, the first surface of the first desiccant solutionchannel is thermally coupled to the first surface of the centralchannel, and the first surface of the second desiccant solution channelis thermally coupled to the second surface of the central channel. 16.The absorber of claim 11, wherein the absorption of water from theprocess air nearby the first membrane and the second membrane causes theprocess air to heat the heat exchange fluid being communicated throughthe heat exchange channel.
 17. A method for dehydrating air using theabsorber of claim 10, the method comprising: communicating a firstportion of the working solution through the first desiccant solutionchannel and a second portion of the second desiccant solution channel;disposing process air nearby the first membrane and the second membranesuch that water vapor is absorbed from the process air into the firstand second portions of the desiccant solution; and communicating a heatexchange fluid through the central channel such that, during theabsorption of water from the process air, the process air can heat theheat exchange fluid.
 18. The method of claim 17, wherein the desiccantcomprises an ionic liquid selected from among1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide,1-ethyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)amide,tetra-nbutylphosphonium trifluoromethanesulfonyl leucine, andN-alkyl-N,N-dimethylhydroxyethylammoniumbis(trifluoromethane)sulfonylimide.
 19. A liquid desiccant dehumidification system (LDDS)comprising: an absorber configured to communicate water vapor from ahumid air flow into a first concentrated desiccant solution to form adilute desiccant solution, the first concentrated desiccant solutioncomprising an aqueous solution of at least one ionic liquid and beingcapable of absorbing water; a first heat exchanger thermally coupled tothe dilute desiccant solution such that heat of the concentrateddesiccant solution generated in the desorption process can be exchangedwith the dilute solution, thereby increasing the temperature of thedilute solution and decreasing the temperature of the concentratedsolution; a first desorber fluidically coupled to the absorber andthermally coupled to the first heat exchange medium, the first desorberbeing configured desorb a portion of the water vapor from the dilutedesiccant solution to form an intermediate desiccant solution, the firstdesorber having an operating temperature of between about 140° C. andabout the boiling point temperature of the desiccant; a second heatexchanger thermally coupled to the first desorber such that thermalenergy of the concentrated desiccant solution from the first desorbercan be conducted into the diluted solution from the first heatexchanger; and a second desorber fluidically coupled to the firstdesorber such that the intermediate desiccant solution can becommunicated therebetween and thermally coupled to the second heatexchange medium, the second desorber being configured to desorb aportion of the water vapor from the intermediate desiccant solution toform a second concentrated desiccant solution having substantially thesame concentration of ionic liquid as the first concentrated desiccantsolution.
 20. The LDDS of claim 19, wherein the ionic liquid comprisesat least one from among 1-butyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazoliumbis(trifluoromethyl-sulfonyl)amide, tetra-nbutylphosphoniumtrifluoromethanesulfonyl leucine, andN-alkyl-N,N-dimethylhydroxyethylammoniumbis(trifluoromethane)sulfonylimide.